Although smoking causes serious respiratory diseases and cancers, it is difficult to get smokers to quit smoking. Nicotine is the effective ingredient in cigarettes. Nicotine is a micro-molecular alkaloid which is basically harmless to humans at low dosages. Tar is the major harmful substance in tobacco. Tobacco tar contains thousands of ingredients, dozens of which are carcinogenic.
Cigarette substitutes have used relatively pure nicotine in patches, chewing gum and aerosols. Still disadvantages remain with cigarette substitutes or products for helping smokers to quit smoking.